Diabetes mellitus is a chronic metabolic disorder caused by an inability of a person's pancreas to produce sufficient amounts of insulin, such that the person's metabolism is unable to provide for the proper absorption of sugar and starch. This failure leads to hyperglycemia, i.e. the presence of an excessive amount of analyte within the blood plasma. Persistent hyperglycemia has been associated with a variety of serious symptoms and life threatening long term complications such as dehydration, ketoacidosis, diabetic coma, cardiovascular diseases, chronic renal failure, retinal damage and nerve damages with the risk of amputation of extremities. Because healing is not yet possible, a permanent therapy is necessary which provides constant glycemic control in order to constantly maintain the level of blood analyte within normal limits. Such glycemic control is achieved by regularly supplying external drugs to the body of the patient to thereby reduce the elevated levels of blood analyte.
An external biologically effective drug (e.g., insulin or its analog) was commonly administered by means of multiple, daily injections of a mixture of rapid and intermediate acting drug via a hypodermic syringe. While this treatment does not require the frequent estimation of blood analyte, it has been found that the degree of glycemic control achievable in this way is suboptimal because the delivery is unlike physiological drug production, according to which drug(s) enters the bloodstream at a lower rate and over a more extended period of time.
Improved glycemic control may be achieved by the so-called intensive drug therapy which is based on multiple daily injections, including one or two injections per day of a long acting drug for providing basal drug and additional injections of a rapidly acting drug before each meal in an amount proportional to the size of the meal. Although traditional syringes have at least partly been replaced by drug pens, the frequent injections are nevertheless very inconvenient for the patient, particularly those who are incapable of reliably self-administering injections.
Substantial improvements in diabetes therapy have been achieved by the development of other drug delivery devices, such as insulin pumps, relieving the patient of the need for syringes or drug pens and the administration of multiple, daily injections. Insulin pumps allow for the delivery of insulin in a manner that bears greater similarity to the naturally occurring physiological processes and can be controlled to follow standard or individually modified protocols to give the patient better glycemic control.
In addition, delivery directly into the intraperitoneal space or intravenously can be achieved by drug delivery devices. Drug delivery devices can be constructed as an implantable device for subcutaneous arrangement or can be constructed as an external device with an infusion set for subcutaneous infusion to the patient via the transcutaneous insertion of a catheter, cannula or a transdermal drug transport such as through a patch. External drug delivery devices are mounted on clothing, hidden beneath or inside clothing, or mounted on the body and are generally controlled via a user interface built-in to the device or on a separate remote device.
Drug delivery devices have been utilized to assist in the management of diabetes by infusing drug or a suitable biologically effective material into the diabetic patient at a basal rate with additional drug or “bolus” to account for meals or high analyte values, levels or concentrations. The drug delivery device typically is connected to an infuser, better known as an infusion set by a flexible hose. The infuser typically has a subcutaneous cannula, and an adhesive backed mount on which the cannula is attached. The cannula may include a quick disconnect to allow the cannula and mount to remain in place on the skin surface of the user while the flexible tubing is disconnected from the infuser. Regardless of the type of drug delivery device, blood analyte monitoring is typically required to achieve acceptable glycemic control. For example, delivery of suitable amounts of drug by the drug delivery device requires that the patient frequently determine his or her blood analyte level and manually input this value into a user interface for the external drug delivery device, which then may calculate a suitable modification to the default or currently in-use drug delivery protocol, i.e. dosage and timing, and subsequently communicates with the drug delivery device to adjust its operation accordingly. The determination of blood analyte concentration is typically performed by means of an episodic measuring device such as a hand-held electronic meter which receives blood samples via enzyme-based test strips and calculates the blood analyte value based on the enzymatic reaction. In recent years, continuous analyte monitoring has also been utilized with drug delivery devices to allow for greater control of the drug(s) being infused into the diabetic patients.
In 1993, the landmark Diabetes Complications and Control Trial (DCCT) showed that intensive control of blood glucose not only reduces but also can prevent complications from Type 1 Diabetes. Post-DCCT health care professionals began prescribing a basal and bolus regimen of intensive insulin therapy to patients to help them maintain better glycemic control.
Basal insulin is a constant or near constant dosage of insulin to provide the body with insulin to allow for processing of glucose to maintain the background metabolic function of the body. Basal insulin can be infused via a daily or twice daily dose of long-acting insulin where the insulin's availability and action is formulated to last for an extended period of time. Alternatively, the basal requirements of an individual may be provided by a constant infusion of rapid acting insulin analog via an insulin delivery device. An insulin bolus is a burst of rapid acting insulin to offset either a prandial event or to bring a patient's blood glucose level from hyperglycemia to the desired, target range. Typically, the bolus of insulin may be delivered subcutaneously through an insulin syringe, an insulin pen or via another insulin delivery device such as an insulin pump.
A person in glucose stasis will tend to remain so in the absence of any meal disturbances and if the person's acting basal insulin schedule exactly offsets the person's background metabolic needs for insulin. When there is an excess of basal insulin at work, then the person's blood glucose level will tend to decrease. A deficiency of basal insulin relative to what the person's body requires will result in an increase in blood glucose level. Often, a person is first diagnosed with diabetes upon finding a higher than normal, fasting blood glucose level; this is a sign of insufficient endogenous insulin production.
In the years since the DCCT, patients with type 1 diabetes have often struggled with managing the challenges of intensive insulin therapy. There are myriad variables that both affect a person's insulin requirements and how their dosing should change on a day to day basis and even within a day. In light of the many deficiencies and problems associated with current systems and methods for maintaining proper glycemic control, enormous resources have been put into finding better solutions. It has been contemplated for many years that it should be entirely feasible to couple a continuous glucose monitoring system with an insulin delivery device to provide some level of automation to the management of insulin delivery to people with diabetes. The effort in this domain has ranged from semi-automated systems to fully automated delivery systems; however, most systems have at least some level of user interaction. Further, in any of these systems, the user's role changes from direct actor to supervisor of the automated system. As such, the user requires new and different tools for overseeing such automation. The present disclosure includes novel systems and methods that assist the user in understanding and visualizing what actions automated insulin delivery systems are taking in an effort to maintain the patient's glycemic control.